Dialkali salts of orthosilicic acid diesters and their preparation

ABSTRACT

Dialkali salts of orthosilicic acid diesters, e.g. disodium orthosilicic acid dimethyl ester, are obtained by reaction of an alkali hydroxide with an orthosilicic acid tetraester. The dialkali salts of orthosilicic acid diesters are useful products for surface treatment of glass plates or glass fibers by tackling or etching.

United States Patent Termin et al.

[451 July 25,1972

DIALKALI SALTS OF ORTHOSILICIC ACID DIESTERS AND THEIR PREPARATIONinventors: Erich Termin, Laufenburg; Walter Rogler,

Bonn; Wilhelm Joch, Niederkassel; Rudiger Honigschmid-Groscich, Ranzel,all of Germany Assignee: Dynamit Nobel AG, Froisdorf, Germany Filed:Oct. 27, 1970 Appl. No.: 84,461

Foreign Application Priority Data Oct. 31, 1969 Germany ..P 19 54 830.2Sept. 30, 1970 Germany ..P 20 48 018.6

U.S. Cl. ..260/448.8, 260/448.8 A

Int. Cl. ..C07f 7/04 Field of Search ..260/448.8 A, 448.8 R

Primary Examiner-Tobias E. Levow Assistant ExaminerWerten F. W. BellamyAttorneyBurgess, Dinklage & Sprung [57] ABSTRACT Dialkali salts oforthosilicic acid diesters, e.g.' disodium orthosilicic acid dimethylester, are obtained by reaction of an alkali hydroxide with anorthosilicic acid tetraester. The dialkali salts of orthosilicic aciddiesters are useful products for surface treatment of glass plates orglass fibers by tackling or etching.

5 Claims, No Drawings DIALKALI SALTS F ORTI-IOSILICIC ACID DIESTERS ANDTHEIR PREPARATION The present invention relates to novel ester salts oforthosilicic acid and to a process for their preparation.

In accordance with the invention dialkali salts of orthosilicic aciddiesters are prepared by the reaction of tetraesters of orthosilicicacid with alkali hydroxides. Preferably the reaction involves alkalimetal hydroxides and tetraalkyl esters of orthosilicic acid,advantageously wherein the alkyl groups have one to four carbon atoms;the products can be understood as being organo-oxosilanolates or asdialkali dialkoxy orthosilicates.

The compounds are salt-like and have crystalline X-ray patterns withwell-defined plane spacing. The compounds are stable up to about 200 to250 C. and above this temperature the alkoxide groups of the ester splitoff as the corresponding ethers or olefins and alcohol, confirming thepresence of alkoxy groups in the compounds.

The compounds of the invention are hydroscopic and hydrolyze tosilicates with the evolution of alcohol. The salts are highly soluble inthe alcohol corresponding to their alkoxy groups.

The reaction proceeds according to the equation:

wherein Me is preferably an alkali metal, and

R is preferably an alkyl radical of one to four carbon atoms,

both alkyl radicals preferably being the same.

A number of different procedures can be used for effecting the reaction.

In one procedure, a several-fold to ten-fold excess of the orthosilicicacid ester is taken as the starting material and the alkali metalhydroxide is added either in solid form or in alcoholic solution.

The reaction starts up at room temperature and heats the mixtureexothermically, although additional heat input may be required. Pressureand temperature are maintained such that first the alcohol and then theexcess of the ester drawn off. In general the procedure is performed attemperatures between the boiling temperature of the pure alcohol andabout 200 C. and at pressures of l to 760 mm Hg.

The alkali hydroxide is thoroughly dried and the ester is used in highlypure state, moisture being excluded.

in order to maintain the speed of the reaction until the reaction hasgone to completion, it is advantageous continuously to distill off thealcohol formed in the reaction, which simultaneously provides a means ofmonitoring the reaction.

After the reaction is complete, careful evaporation of the excessalcohol and ester yields free-flowing white powders which, from theiranalyses, are the alkali salts of the trialkyl silicic acid, having thegeneral formula MeO Si (OR) From these intermediates the dialkali saltsof the orthosilicic acid dialkyl esters, (MeO) Si(OR) are obtained bytreatment with heat or by extraction with solvents. The heat treatmentis generally performed at l to 20 mm Hg. and at an elevated temperaturefrom about l50 to 230 C., with stirring and continuous removal of Si(OR)by suction filtering or distillation.

The dialkali salts can also be obtained by combining the ortho ester andalkali hydroxide starting products in a molar ratio of l 2, i.e., 2moles of alkali hydroxide in alcoholic solution or solid form are addedto 1 mole of the ortho ester.

The procedure is especially advantageous in the preparation of thealkali salts of the silicon esters of alkanols of two to four carbonatoms because only the lower boiling alcohols have to be evaporated inorder to purify them as shown in Examples 4 to 9 hereinbelow.

Another method of preparation consists in adding the orthoester, plainor dissolved, to an alcoholic solution of the alkali hydroxide (Example10 hereinbelow). The yield of the dialkali salts is virtuallyquantitative based on the alkali hydroxide input.

The invention will be illustrated in the following examples wherein,unless otherwise specified, all parts and percentages are by weight.

EXAMPLE in One thousand g of Si(OCH;,) were put into a reaction vcs seland then 60 g of NaOH (dried at 500 C.) were added. The formation of asalt began immediately in an exothermic reaction, with the formation ofmethanol. With further heating the methanol that formed was continuouslydistilled from the mixture. After about 30 minutes the reaction hadended; the boiling temperature remained constant at l2l C. correspondingto that of pure Si( OCH The salt that had formed was contained in theester largely in the form of a suspension. The excess ester was thendistilled off and the salt residue was dried at 60 C. and 20 mmHg to afree-flowing, white, odorless powder. Two hundred and thirtysix g of thesalt residue and 834 g of distillate were obtained from the reaction,94.2 percent of the distillate consisting of Si(OCH and 5.8 percentconsisting of methanol.

The salt residue obtained as intermediate corresponded in analysis tothe monosodium salt of orthosilicic acid trimethyl ester.

EXAMPLE lb Two hundred g of the salt product of la was further heated at20 mm Hg and when the temperature reached I55 C. Si(OCH was distilledoff, this continuing during the further heating of the salt to 230 C. At230 C./2() mm Hg there remains a crystalline, white salt which, on thebasis of quantitative and qualitative analysis, corresponds to thedisodium salt oforthosilicic acid dimethyl ester.

The distillate (93.5 g) consisted of 100% Si(OCH The salt residueobtained 106 g) gave the following analysis:

27.2% sodium 16.6% silicon 34.9% OCH These values are in good agreementwith the theoretical values for the compound (NaO) Si(OCH;,)

The density of the compound in petroleum amounts to l.374 g/ml. Theresidue on ignition was 76.5 wt-7c at 550 C. and 73.8 wt-% at 800 C.

The substance is soluble in lower alcohols, especially methanol, butinsoluble in most other solvents.

The presence of moisture results in hydrolysis.

X-ray study showed lattice plane spacings of 3.35 A, 6.3 l A and l2.36A.

Upon further heating of the prepared salt to temperatures above 230 C.at 20 mm Hg, dimethyl ether is given off, which is attributed to acondensation between methoxy groups with the formation of Si-O-Si bonds.

EXAMPLE it The salt residue of Example In was exhaustively extractedwith carbon tetrachloride at C. In this manner a salt was obtainedhaving the same analytical values and characteristics as the one inExample lb.

In a manner analogous to Examples la to lc, Si(OC H can be reacted withNaOH or KOH.

EXAMPLE 2a One thousand g Si(OCH were put into a reaction vessel and 80g of KOH, dried at 500 C. were added. The reaction proceeded as inExample la. There were obtained 243 g of a salt residue comprising awhite free-flowing powder, and 836 g of a distillate which consisted of94.5% Si(OCH and 5.4% methanol.

The salt residue had the following analysis:

23.1% potassium 154% silicon 49.5% OCH 19.1% C 4.9% H

EXAMPLE 2b Two hundred g of the salt prepared under 2a were heated at 20mm Hg and 230 C. As in Example 1b, the distillation of Si(OCH left acrystalline, white salt which, according to qualitative and quantitativeanalysis, corresponds to the dipotassium salt of orthosilicic aciddimethyl ester. Analysis:

39.6% potassium 14.3% silicon 30.1% OCH These percentages are inagreement with the formula (KO) Si(OCH;,

The density ofthe compound in petroleum at 20 C. is 1.473 g/ml. Theignition residue was determined to be 75.1 wt-% at 550 C. and 71.2 wt-%at 800 C.

X-ray examination showed lattice plane spacings of 3.35 A, 5.48 A and10.26 A. Like the disodium salt, the dipotassium salt of orthosilicicacid dimethyl ester yields dimethyl ether when heated above 230 C. at 20mm Hg, which is to be attributed to the condensation of OCH groups.

EXAMPLE 2c The salt residue of Example 2a was dissolved by the steadyaddition of methanol at the boiling point, and Si(OCH was removed by thesteady distillation of the methanol. As soon as no more Si(OCH occurredin the distillate, the remainder of the methanol was evaporated away.The residue had the precise composition of the compound (KO) Si(OCH andthe same characteristics as above.

EXAMPLE 3 Analogously to Example In and 2a, dried LiOH was reacted withSi(OCH The volume-time yield of the reaction of Si(OCH with LiOH amountsto approximately one onehundredth that with NaOH or KOH as in Examples111 and 2a, respectively.

EXAMPLE 4 One Thousand g of Si(OC H were placed in a reaction vessel andsuccessively a solution of 384 g NaOH (dehydrated at 500 C.) and 2,000 gof ethanol were added. During the addition of these substances themixture was heated to boiling with refluxing. Thereafter the clearsolution was heated for about 1 more hour, with refluxing, and then theethanol was evaporated away and the salt residue, a white free-flowingpowder, was dried at 150 C. and 1 mm Hg. The amount of ethanol removedby the evaporation was 2442 g, in which no more (Si(OC H could bedetected; the salt residue amounted to 940 g and corresponded, as shownby the following analysis, to the disodium salt of orthosilicic aciddiethyl ester ofthe formula (NaO) Si(OC H,,)

23.3% sodium 14.1% silicon 45.5% OC H The density of the compound inpetroleum at C. amounts to 1.37. The ignition residue was determined tobe 63.7 wt'-% at 550 C. and-61.7 wt-% at 800 C.

X-ray analysis showed lattice plane spacings of 2.08 A, 3.42 A and 15.30A.

When the disodium salt of silicic acid diethyl ester is heated to above210 C. at 10 mm Hg, ethylene, ethanol, methane and C0 are given off,which is attributed to decomposition of the salt.

EXAMPLE 5 One thousand g of Si(OC H were reacted with 539 g of KOHdissolved in 3,300 g of ethanol in a procedure and under conditionsanalogous to Example 4, and then a salt residue was obtained from theclear reaction solution by evaporating the ethanol at C. and 1 mm Hg.3,743 g of ethanol were evaporated, in which no more Si(OC,H,-,), couldbe detected. The salt residue, a white free-flowing powder, amounted to1,093 g and, with the following analysis, corresponded to thedipotassium salt oforthosilicic acid diethyl ester (KO) Si(OC H.021

33.4% potassium 12.3% silicon 38.9% OC H The density of the compound inpetroleum at 20 C. amounts to 1.43. The ignition residue was determinedto be 71.2 wt-% at 550 C. and 66.5 wt-% at 800 C. X-ray examinationshowed lattice plane spacings of 3.40 A and 1 3.32 A.

When the dipotassium salt of the silicic acid diethyl ester is heated toabove 210 C. at 10 mm Hg, ethylene, ethanol, methane and C0 are givenoff due to decomposition.

EXAMPLE 6 One thousand g of Si(OC -,H were placed in a reaction vesseland a solution of 303 g of NaOH in 2,100 g n-propanol was added inincrements, with heating, over a period of about 30 minutes. After theadding ofthis solution, the clear solution was refluxed for about 1hour, and then the propanol was evaporated and the salt residue wasdried at 150 C. and 1 mm g g 2,550 g of n-propanol was obtained asdistillate, in which Si( OC,,H,b4 could no longer be detected. Theresidue, a white free-flowing powder, amounted to 851 g and, with thefollowing analysis, virtually corresponded to the disodium salt oforthosilicic acid dipropyl ester of the formula (NaO) Si(OC,-, r)2

20.6% sodium 13.1% silicon 53.0% OC H The density of this compound,measured in petroleum, at 20 C. amounted to 1.28. The ignition residuewas determined to be 58.5 wt-% at 550 C. and 53.8 wt-% at 800 C. X-rayexamination showed lattice plane spacings of 3.41 A and 16.28 A.

Heating of the disodium salt of the silicic acid dipropyl ester totemperatures above 200 C. yields propylene, propanol, methane and CO dueto decomposition of the salt.

EXAMPLE 8 One thousand g of Si(OC,H,,) were placed in a reaction vesseland heated, and then a solution of 250 g of NaOH in 2,500 g of n-butanolwas added. After the clear solution had been refluxed for about 1 hour,2,960 g of C,H,,OH in which Si(OC,,H,,b4 could no longer be detected wasdrawn off while the solution was heated up to C. at 1 mm Hg. Sevenhundred and ninety g of a yellowish white free-flowing powder wasobtained as the salt residue.

The analysis corresponds to the disodium salt of orthosilicic aciddibutyl ester NaO) Si(OC,,H,,)

l 7.9% sodium 1 1.1%silicon The density of the compound measured inpetroleum amounts to 1.14.

The ignition residue was determined to be 61.1 wt-% at 550 C. and 47.9wt-% at 800 C.

X-ray examination showed lattice plane spacings of 3.40 A and 16.28 A.

When the disodium salt of the silicic acid dibutyl ester is heated totemperatures above 200 C., butanol, olefin, methane and C0 are given offdue to decomposition of the salt.

EXAMPLE 9 One thousand g of Si(OC,,H,,) were reacted with 350 g of KOHdissolved in 3,500 g of n-C,H OH under experimental conditions analogousto those of Example 8.

After the reaction had ended, 3,960 g of n-butanol containing no moredetectable Si(OC ,H,,) was withdrawn when the solution was heated to 150C. at 1 mm Hg. The salt residue was 890 g of a white free-flowing powderwhich, according to the following analysis, corresponded to thedipotassium salt of orthosilicic acid dibutyl ester (KO) Si(OC H,,)

27.2% potassium 9.9% silicon 52.3% OC H,,

The density of the salt, measured in petroleum, amounts to 1.24.

The ignition residue was determined to be 60.7 wt-% at 550 C. and 53.8wt-% at 800 C.

The X-ray examination showed lattice plane spacings of 3.42 A and 16.28A.

When the dipotassium salt of the silicic acid dibutyl ester was heatedto temperatures above 200 C., butanol, olefin, methane and CO wereformed as a result of decomposition of the product.

EXAMPLE l0 Sixty g of NaOH (dehydrated at 500 C.) were dissolved in 300g of CH OH and the solution was refluxed. Upon the addition of Si(OCH awhite precipitate settled out.

A total of 1 13 g of Si(OCH;,) was added successively over a period of 3hours, corresponding to a 2 1 molar ratio of NaOH Si(OCH Then thesuspension was filtered, the salt residue was washed with methanol andwas dried at C./ 1 mm Hg.

The composition of the residue (37 g) corresponded approximately to asodium metasilicate, on the basis of the following analysis:

OCH,-,0.94%

The filtrate was concentrated by evaporation, whereupon a salt residue(60g) was obtained which, when dried at 230 C./20 mm Hg, corresponded tothe disodium salt of orthosilicic acid dimethyl ester (NaO) Si(OCH 27.9%sodium 16.6% silicon 35.1%OCH,,

The distillate consisted of 95.8% CH;,OH and 4.2% a)4l:

The novel dialkali salts of orthosilicic acid diesters of the inventionare useful products for surface treatment of glass plates or glassfibers by tackling or etching.

What is claimed is:

1. Dialkali salts of orthosilicic acid lower alkyl diesters.

2. Esters according to claim 1, wherein Me is sodium or potassium andboth R radicals are the same alkyl of one to four carbon atoms.

3. Process for the production of diesters according to claim 1 whichcomprises reacting an alkali hydroxide with an orthosilicic acid loweralkyl tetraester.

4. Process according to claim 3, wherein the alkali metal hydroxide issodium or potassium hydroxide and the alkyl groups of the tetra-loweralkyl ortho-silicate are the same alkg l of one to four carbon atoms.

. Process according to claim 4, wherein the reaction 18 carried outsubstantially under anhydrous conditions.

11mm saw was warren? 0mm CERT] FE 1A.] lg; OF "(JUEXHEC'Yi UN Patent No.3 7 ,7 4 Dated July 25 1972 '.[nventor(s) Erich Termin 'et a1 It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

First Page ,box [73] Assiggee change "Froisdorf" to -'-Troisd Col. 1,line 40, before ester, insert --can be--.

Col. 3 line 18, change the formula from "(KO) Si( 0CH to --(K O) S1(OCHCol. 3 line 57, change '.'(S1'.(OC H 2 to --Si(OC H Col. 4, line 36',change "Si.(OC H b4" to -Si(OC H Col. 4 line 61 change "Si(0C H b4" to--Si(OC H I n H Col. 6 l ne 21, change S1 (OCH to S 1(OCH Signed andsealed this 9th day of January 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROB ERT GOTTSCHALK Attesting Officer Commissionerof Patents

2. Esters according to claim 1, wherein Me is sodium or potassium andboth R radicals are the same alkyl of one to four carbon atoms. 3.Process for the production of diesters according to claim 1 whichcomprises reacting an alkali hydroxide with an orthosilicic acid loweralkyl tetraester.
 4. Process according to claim 3, wherein the alkalimetal hydroxide is sodium or potassium hydroxide and the alkyl groups ofthe tetra-lower alkyl ortho-siLicate are the same alkyl of one to fourcarbon atoms.
 5. Process according to claim 4, wherein the reaction iscarried out substantially under anhydrous conditions.